Recently, a number of studies and developments have been performed on metal complex compounds for preparing materials employed in the fields of semi-conductors, electronic elements and optical elements. For instance, complex compounds of metals described in Periodic Table IIA (e.g., strontium, barium and magnesium) are employed and studied as materials for manufacturing ferro-dielectrics and super-conductive elements or materials for preparing a protective film of a plasma display device. Complex compounds of metals described in Periodic Table IIB (e.g., zinc) are employed and studied as materials for manufacturing light-transmitting electro-conductive films and light-emitting elements. Complex compounds of metals described in Periodic Table IIIB (e.g., indium, aluminum, and gallium) are employed and studied as materials for manufacturing light-transmitting electro-conductive films and insulating films of semi-conductor memory gate.
Complex compounds of metals described in Periodic Table IVB (e.g., tin and lead) are employed for manufacturing light-transmitting electro-conductive film and ferro-dielectrics. Complex compounds of metals described in Periodic Table VA (e.g., vanadium) are studied for the purpose of preparing ferro-dielectrics and barrier films for copper wiring of silicon semi-conductors.
Complex compounds of metals described in Periodic Table IVA (e.g., titanium, zirconium and hafnium) are employed for preparing ferro-dielectrics (PZT) and barrier films for copper wiring of silicon semi-conductors. Complex compounds of metals described in Periodic Table VIA (e.g., chromium) are employed for preparing glass for an optical fiber laser and coating of steel surface. Complex compounds of metals described in Periodic Table VIIA (e.g., manganese) are employed and studied as materials for preparing electrochromism devices and further employed and studied as materials for preparing thermistors due to their wide variation of resistance with temperature and wide temperature resolution. Complex compounds of metals described in Periodic Table VIII (e.g., nickel and cobalt) are studied for preparing films used on silicon semi-conductors for increasing density of copper nuclei generation in copper wiring and increasing adhesion of copper wiring to an under-lying layer.
Complex compounds of metals described in Periodic Table IB (e.g., copper, silver, and gold) are used for manufacturing electro-conductive wiring for the reason that these metals show low electric resistance. Particularly, a number of studies have been conducted on a copper film, because a copper film is employable for manufacturing wiring of silicon semi-conductors. A metal oxide film comprising copper oxide is paid attention as material of a high-temperature super-conductive elements.
Rare earth metals (e.g., scandium, yttrium, and lanthanoids) are paid attention as materials for preparing high-temperature super-conductive element, high dielectrics for a gate insulating film and ferro-dielectrics for PLZT film. Accordingly, the complex compounds of rare earth metals are of value for preparing these materials.
The metal films and metal oxide films are conventionally prepared by the CVD method, because the CVD method can easily give a thin film with uniform thickness Therefore, materials favorably employable in the CVD method are required.
At the present time, metal complex compounds having a β-diketonato ligand are widely employed as materials for preparing a metal atom-containing film by the CVD method. The metal complex compounds having a β-diketonato ligand are good in their stability and sublimation property, and hence are of value as the metal sources for the CVD method. Representative example of the β-diketonato ligands are acetylacetonato (acac) and 2,2,6,6-tetra-methyl-3,5-heptanedionato (dpm).
It is noted that most of known metal complex compounds having a β-diketonato ligand are solid at an ordinary temperature and have a high melting temperature. Therefore, the use of the known metal complex compounds as the metal source in the CVD method is liable to cause plugging in the pipe systems for supplying a metal source, and is not satisfactorily accepted in industry.
For the reason mentioned above, a number of studies have been made for obtaining metal complex compounds having good stability and a low melting temperature. One of the known improvements resides in the attachment of an ether bonding-containing substituent group to the β-diketonato ligand to obtain a metal complex compound having a satisfactory stability and a low melting temperature.
For instance, Patent publication 1 and Non-patent publication 1 (mentioned afterward) describe complex compounds of strontium (described in Periodic Table IIA) having the following formulas (a) and (b):

It is noted that the strontium complex compound of the formula (a) shows improved stability but unfortunately shows a low vapor pressure, and that the strontium complex compound of the formula (b) shows good stability and good sublimation, but unfortunately has a high melting point (235° C.). Therefore, it appears that these complex materials are not favorably employed for the preparation of a strontium film by the CVD method.
Non-patent publication 2 (mentioned afterward) describes a complex compound of zinc (described in Periodic Table IIB) having the following formula:

It is noted that the above-mentioned zinc complex compound shows a low thermal stability and easily suffers thermal deterioration. Therefore, it is not easy to supply the zinc complex compound with no troubles.
Patent Publication 2 (mentioned afterward) describes a complex compound of aluminum (described in Periodic Table IIIB) having an ether group-containing ligand which is illustrated below:

It is noted that the above-mentioned aluminum complex compound shows low thermal stability and hence easily suffers thermal deterioration. Therefore, it is not easy to supply the aluminum complex compound with no troubles.
There are known no studies in connection with gallium complex compounds and indium complex compounds.
Patent Publication 3 (mentioned afterward) describes Sn(dpm)2 as a complex compound of tin (described in Periodic Table IVB). It is noted that the tin complex compound is very sensitive to water. Therefore, it is not easy to handle this tin complex compound.
As for the lead complex compounds, Patent Publications 4 and 5 (mentioned afterward) describe Pb(dmp)2 and bis(1,3-diphenyl-1,3-propanedionato)lead(II). It is noted that these complex con-pounds have a high melting point. Therefore, these complex compounds are not satisfactorily employable for the preparation of a lead film by the CVD method.
As for the complex compound of vanadium (described in Periodic Table VA), Patent Publication 6 (mentioned afterward) describes V(dpm)2. It is noted that this complex compound also has a high melting point. Therefore, this complex compound is not satisfactorily employable for the preparation of a vanadium film by the CVD method.
As for the complex compound of nickel (described in Periodic Table VIII), Non-patent Publication 2 and Patent Publication 7 (mentioned afterward) describe a metal complex compounds having the following formulas (c) and (d):

It is noted that the nickel complex compound of the formula (c) shows poor thermal stability and easily suffers thermal deterioration, and that the nickel complex compound of the formula (d) shows a low vapor pressure due to its high molecular weight.
As for the cobalt complex compound, Patent Publication 8 (mentioned afterward) describes a metal complex compound having the following formula:

It is noted that the above-mentioned cobalt complex compound shows poor thermal stability and easily suffers thermal deterioration. Therefore, it is not easy to supply the cobalt complex compound with no troubles.
As for the copper complex compound, Patent Publication 9 (mentioned afterward) describes a copper complex compound having the following formula:
in which R is isopropyl or tert-butyl, R1 is methyl or ethyl, and R2 is propyl or butyl
It is noted that the above-mentioned copper complex compound shows no improvement in its rate of copper film formation. Therefore, it is not satisfactorily employable due to its low productivity.
As for the complex compounds of rare earth metals, Patent Publications 10 to 12 describe metal complex compounds having the following formula:
in which REM stands for a rare earth metal atom, R1 is isobutyl or t-butyl, and R2 is isopropyl, isobutyl, t-butyl, 1-ethylpentyl or 2-(2-methoxyethoxy)-1,1′-dimethylethyl.
It is noted that the above-mentioned rare earth metal complex compounds have a high melting point and is insoluble or sparingly soluble in organic solvents. Further, the film formation needs a high temperature operation.                Patent Publication 1: JP-A-9-136857        Patent Publication 2: DE-A-2207866        Patent Publication 3: JP-A-6-234779        Patent Publication 4: JP-A-2002-155008        Patent Publication 5: JP-A-2003-226664        Patent Publication 6: JP-A-2003-49269        Patent Publication 7: WO 01/48130        Patent Publication 8: JP-A-2-121944        Patent Publication 9: JP-A-2001-181840        Patent Publication 10: JP-A-2003-321475        Patent Publication 11: JP-A-4-72066        Patent Publication 12: JP-A-9-228049        Non-patent Publication 1: Zhurnal Neorgaicheskoi Khimiii, 36(9), 2279 (1991)        Non-patent Publication 2: Inorg. Chem., 1(2), 404 (1962)        